Cyclone separators are used in different applications where solid particulates suspended in a gas phase are to be separated from the gas phase. A separator typically comprises a cyclone housing having an upper substantially cylindrical part with an upwardly extending circular discharge for the gas phase, a lower conical part having an outlet at its narrow bottom for discharging particulate matter, a tangential inlet in the upper part for introducing the suspension which is to be separated, and a central circular structure called a thimble depending from a shelf at an upper wall of the housing. The thimble (which can also be referred to as a central tube, a vortex finder or a dip tube) is adjacent the outlet and extends from the shelf axially in the cyclone housing to a distal free open end. The thimble forces the incoming suspension to rotate around the outside of the cyclone creating rotation and a vortex in the center of the cyclone allowing gas to exit upwardly through the discharge duct and obstructs particulate matter from exiting upwardly so that the particulate matter exits through the outlet at the bottom of the conical part.
U.S. Pat. Nos. 4,505,051 and 7,841,477 describe cyclone separators; the contents of these patents and the contents of the patents cited in these patents are incorporated herein by reference.
Cyclone separators such as used in cement making plants operate at very high temperature, approaching 1000 degrees C. for example, and are exposed to corrosive materials. These harsh environments can degrade the thimble to a condition requiring its replacement long before the end of the working life of the cyclone separator.
Replacement of a thimble has been an expensive proposition in part because a new premium thimble will typically be custom built for a specific installation. Experienced suppliers, to reduce costly manufacturing mistakes, will often visit the prospective site of a repair or upgrade to closely verify the geometry of the separator to assure that the replacement thimble to be manufactured will fit the separator unit when it is delivered. This field study adds to basic costs and extends the delivery time of a replacement thimble.
Heretofore, premium replacement thimbles have been custom built, often on a rush basis, after a failure or the detection of an insipient failure. The aftermarket industry has generally not found it practical to build and inventory complete thimble units because of the variety of separator sizes in installed plants.
Cyclone separators operating at high temperature and subjected to corrosive materials have been susceptible to early thimble degradation in part, because of relatively large exposed metal areas. Prior thimble designs have been relatively expensive to manufacture, for example, because segments making up the circular thimbles were made with arcuate shapes that complicated their tooling, molding, and assembly.